Multicast routing method and an apparatus for routing a multicast packet

ABSTRACT

A communication unit is connected to both an IPv4 network and an IPv6 network for converting an IPv4 multicast packet into an IPv6 multicast packet. The communication unit, which has held the IPv6 multicast addresses, holds the IPv4 multicast addresses of a multicast group on the IPv4 network and the held IPv6 multicast addresses in correspondence with each other. Moreover, the communication unit converts the IPv4 multicast address of the received IPv4 multicast packet into the IPv6 multicast address held in correspondence with the IPv4 multicast address, then transmits the multicast packet to the IPv6 network.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation application of U.S. Ser. No. 09/865,580 filed onMay 29, 2001.

This application relates to U.S. patent application Ser. No. 09/257,003filed on Feb. 25, 1999 based on Japanese Patent Application Number10-046739 filed on Feb. 27, 1998, U.S. patent application Ser. No.09/614,715 filed on Jul. 6, 2000 based on Japanese Patent ApplicationNumbers 8-291480 and 9-212889, and U.S. patent application Ser. No.09/421,275 filed on Oct. 20, 1999 based on Japanese Patent ApplicationNumber 10-299613, all of which are assigned to the present assignee. Thecontents of those applications are incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to an IPv4-IPv6 multicast communicatingmethod and an IPv4-IPv6 multicast communicating apparatus in acommunications network system. More particularly, it relates to a methodand an apparatus for implementing the multicast communication between anIPv4 terminal using IPv4 (i.e., Internet Protocol Version 4) as thecommunications protocol and an IPv6 terminal using IPv6 (i.e., InternetProtocol Version 6) as the communications protocol.

As one example of the methods for implementing the communication betweenthe IPv4 terminal and the IPv6 terminal, there can be cited a technologydisclosed in U.S. Pat. No. 6,118,784 (JP-A-11-55319). This technologyallows the communication between the IPv4 terminal and the IPv6 terminalin the following way: An IP address conversion table for managing thecorrespondence between an IPv4 address and an IPv6 address is createdusing DNS (i.e., Domain Name System) protocol extending technology in anapparatus located halfway in the communications path. Then, based on theIP address conversion table, an IPv4 header-IPv6 header conversion isexecuted, thereby allowing the communication to be implemented.

SUMMARY OF THE INVENTION

The above-cited prior art makes it possible to implement an IP unicastcommunication between the IPv4 terminal and the IPv6 terminal. In thisprior art, however, no consideration has been given to the IP multicastcommunication between the IPv4 terminal and the IPv6 terminal.

It is an object of the present invention to provide a method ofexecuting the IP multicast communication between the IPv4 terminal andthe IPv6 terminal, and an apparatus for enabling the IP multicastcommunication to be executed.

It is another object of the present invention to provide a method ofpermitting the IPv6 terminal to receive an IP multicast packettransmitted from the IPv4 terminal, and an apparatus for enabling thereception to be executed.

It is still another object of the present invention to provide a methodof permitting the IPv4 terminal to receive an IP multicast packettransmitted from the IPv6 terminal, and an apparatus for enabling thereception to be executed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates the configuration diagram of a converting apparatusaccording to a 1st embodiment of the present invention;

FIG. 2 illustrates the configuration diagram of an IPv4 unicast addresstable;

FIG. 3 illustrates the configuration diagram of an IPv4 multicastaddress table;

FIG. 4 illustrates the configuration diagram of an IPv6 unicast addresstable;

FIG. 5 illustrates the configuration diagram of an IPv6 multicastaddress table;

FIG. 6 illustrates the configuration diagram of the IP addressconversion table;

FIG. 7 illustrates the configuration diagram of an IPv4 multicastmembership table;

FIG. 8 illustrates the configuration diagram of an IPv6 multicastmembership table;

FIG. 9 illustrates the configuration diagram of a communications networksystem according to the 1st embodiment of the present invention;

FIG. 10 illustrates a flowchart in the case where an IP multicast packetbroadcast (transmitted) by an IPv4 multicast server is received by anIPv6 multicast client through the converting apparatus according to the1st embodiment of the present invention;

FIG. 11 illustrates a flowchart subsequent to the one in FIG. 10;

FIG. 12 illustrates the configuration diagram of a communicationsnetwork system according to an embodiment differing from the 1stembodiment of the present invention;

FIG. 13 illustrates an example of the hardware configuration diagram ofthe communicating apparatus according to the present invention; and

FIG. 14 illustrates formats of the IPv6 header and the IPv4 header.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, referring to the drawings, the explanation will be givenconcerning the embodiments of the present invention. Incidentally, theembodiments set no limitations to the present invention.

FIG. 1 illustrates the configuration diagram of a converting apparatus 1a according to the 1st embodiment of the present invention. Theconverting apparatus 1 a, which is positioned between an IPv4 network101 and an IPv6 network 102, executes the IP header conversion mutuallybetween an IPv4 multicast packet and an IPv6 multicast packet. Based onthis IP header conversion processing, the converting apparatus 1 aimplements the IP multicast communication between the IPv4 terminal andthe IPv6 terminal. As illustrated in FIG. 1, the converting apparatus 1a includes an IP transmitting/receiving unit 2, a for-conversion IPaddress holding unit 3, an IP address conversion information holdingunit 4, an IP multicast membership group managing unit 5, and an IPheader converting unit 6.

The IP transmitting/receiving unit 2 performs thetransmittance/reception of the IPv4 multicast packet with the IPv4network 101, and the transmittance/reception of the IPv6 multicastpacket with the IPv6 network 102.

The for-conversion IP address holding unit 3 holds an IPv4 unicastaddress, an IPv4 multicast address, an IPv6 unicast address, and an IPv6multicast address, all of which are used for the IP header conversion.An IPv4 unicast address table 31 holds the IPv4 unicast address used forthe IP header conversion. In this embodiment, the IP addresses to beheld by the for-conversion IP address holding unit 3 have beenregistered in advance in accordance with the instruction from a managerof the converting apparatus 1 a. In addition to this method, thefollowing method is also allowable: The converting apparatus performsthe communication with a DHCP server so as to automatically acquireunused addresses, then holding the unused addresses into thefor-conversion IP address holding unit 3. An IPv4 multicast addresstable 32 holds the IPv4 multicast address used for the IP headerconversion. An IPv6 unicast address table 33 holds the IPv6 unicastaddress used for the IP header conversion. An IPv6 multicast addresstable 34 holds the IPv6 multicast address used for the IP headerconversion. The for-conversion IP address holding unit 3 holds andmanages all of the IPv4 unicast address table 31, the IPv4 multicastaddress table 32, the IPv6 unicast address table 33, and the IPv6multicast address table 34.

The IP address conversion information holding unit 4 holds the IPv4unicast address and the IPv6 unicast address, and the IPv4 multicastaddress and the IPv6 multicast address in a state of being made tocorrespond to each other, respectively. The IP address conversioninformation holding unit 4 converts the IPv4 multicast address into theIPv6 multicast address held in correspondence with the IPv4 multicastaddress. Here, the IPv4 multicast address is an IPv4 transmissiondestination address of the IPv4 multicast packet broadcast (transmitted)by the IPv4 terminal on the IPv4 network 101. Moreover, the IP addressconversion information holding unit 4 converts the IPv4 unicast addressinto the IPv6 unicast address held in correspondence with the IPv4unicast address, the IPv4 unicast address being an IPv4 transmissionsource address of the above-described IPv4 multicast packet.

Also, the IP address conversion information holding unit 4 converts theIPv6 multicast address into the IPv4 multicast address held incorrespondence with the IPv6 multicast address. Here, the IPv6 multicastaddress is an IPv6 transmission destination address of the IPv6multicast packet broadcast (transmitted) by the IPv6 terminal on theIPv6 network 102. Moreover, the IP address conversion informationholding unit 4 converts the IPv6 unicast address into the IPv4 unicastaddress held in correspondence with the IPv6 unicast address, the IPv6unicast address being an IPv6 transmission source address of theabove-described IPv6 multicast packet.

An IP address conversion table 41 holds the following addresses,respectively: The IPv4 transmission destination address of the IPv4multicast packet, which has been received by the converting apparatus 1a, and the IPv6 multicast address corresponding thereto, and the IPv4transmission source address of the above-described IPv4 multicast packetand the IPv6 unicast address corresponding thereto. Also, the IP addressconversion table 41 holds the following addresses, respectively: TheIPv6 transmission destination address of the received IPv6 multicastpacket and the IPv4 multicast address corresponding thereto, and theIPv6 transmission source address of the above-described IPv6 multicastpacket and the IPv4 unicast address corresponding thereto. The IPaddress conversion information holding unit 4 holds and manages theabove-described IP address conversion table 41.

In accordance with the instruction from the manager of the convertingapparatus 1 a, the IP multicast membership group managing unit 5performs the membership state management of the converting apparatus 1 ainto an IPv4 multicast group and an IPv6 multicast group. Also, the IPmulticast membership group managing unit 5 instructs the IP addressconversion information holding unit 4 to register the IPv4 multicastaddress of the IPv4 multicast group of which the converting apparatus 1a is a member and the IPv6 multicast address corresponding thereto, orthe IPv6 multicast address of the IPv6 multicast group of which theconverting apparatus 1 a is a member and the IPv4 multicast addresscorresponding thereto. An IPv4 multicast membership table 51 holds theIPv4 multicast address of the IPv4 multicast group of which theconverting apparatus 1 a is the member. Also, an IPv6 multicastmembership table 52 holds the IPv6 multicast address of the IPv6multicast group of which the converting apparatus 1 a is the member. TheIP multicast membership group managing unit 5 holds and manages the IPv4multicast membership table 51 and the IPv6 multicast membership table52.

The IP header converting unit 6 executes the IP header conversion towardthe IPv4 multicast packet transferred from the IP transmitting/receivingunit 2, thereby creating the IPv6 multicast packet. Furthermore, the IPheader converting unit 6 instructs the IP transmitting/receiving unit 2to send out the created IPv6 multicast packet to the IPv6 network 102.

FIG. 14( a) illustrates an IPv6 header format. The IPv6 header formatincludes the following fields: The version number of IPv6, i.e., “6”, isstored into a “Version” field. The priority of a processing at the timewhen a router relays the packet on a network is stored into a “Priority”field. The identifier at the time of performing a priority control orthe like is stored into a “Flow Label” field. The length of the dataportion resulting from removing the IPv6 header portion from the packetis stored into a “Payload Length” field. The identifier as to the headerof which higher-order layer's protocol will follow next to the IPv6header or the like is stored into a “Next Header Identifier” field. Themaximum transfer number of the packet is stored into a “Hop Limit”field. In addition, the transmission source IP address is stored into a“Transmission Source IP Address” field, and the transmission destinationIP address is stored into a “Transmission Destination IP Address” field.

FIG. 14( b) illustrates an IPv4 header format. The IPv4 header formatincludes the following fields: The version number of IPv4, i.e., “4”, isstored into a “Version” field. The length of the IPv4 header itself isstored into a “Header Length” field. The information indicating theservice quality of a communications processing is stored into a “ServiceType” field. The size of the entire packet resulting from adding theIPv4 header to the data block dealt with in the IP is stored into a“Packet Length” field. The identifier that is used as the referenceinformation when transferring the data to the higher-order layer isstored into an “Identifier” field. The control information on thedivision of the packet is stored into a “Fragment Offset” field. Theinformation indicating where the divided data (i.e., the fragments) havebeen positioned within the original data is stored into a “Flag” field.The time during which the packet may exist on the network is stored intoa “Time To Live” field. The information indicating what the higher-orderlayer's protocol is is stored into a “Protocol” field. The checksum ofthe IP header is stored into a “Header Checksum” field. In addition, thetransmission source IP address is stored into a “Transmission Source IPAddress” field, and the transmission destination IP address is storedinto a “Transmission Destination IP Address” field.

The IP header converting unit 6 executes the processing of convertingthe IPv4 header to the IPv6 header, both of which are illustrated inFIG. 14, or the processing of converting the IPv6 header to the IPv4header. Then, the converting unit 6 sets the values in the respectivefields within the IPv4 or the IPv6 header format after having beenconverted. Incidentally, in the following explanation concerning thepresent embodiment, an attention will be focused on, in particular, theaddress conversion of the transmission source IP address and thetransmission destination IP address out of the IP header conversionprocessing. Accordingly, the description will be given mainly regardingthe conversion processing of the “Transmission Source IP Address” fieldand the “Transmission Destination IP Address” field.

In this IP header conversion, the IP header converting unit 6 makes aninquiry of the IP address conversion information holding unit 4, therebyacquiring the IPv6 multicast address corresponding to the IPv4transmission destination address of the IPv4 multicast packet. Then,using the IPv6 multicast address acquired from the IP address conversioninformation holding unit 4, the IP header converting unit 6 converts theIPv4 transmission destination address into the IPv6 transmissiondestination address. Similarly, the IP header converting unit 6 makes aninquiry of the IP address conversion information holding unit 4, therebyacquiring the IPv6 unicast address corresponding to the IPv4transmission source address of the IPv4 multicast packet. Then, usingthe IPv6 unicast address acquired from the IP address conversioninformation holding unit 4, the IP header converting unit 6 converts theIPv4 transmission source address into the IPv6 transmission sourceaddress.

Furthermore, the IP header converting unit 6 creates the IPv4 multicastpacket from the IPv6 multicast packet transferred from the IPtransmitting/receiving unit 2, then instructing the IPtransmitting/receiving unit 2 to send out the IPv4 multicast packet tothe IPv4 network 101. In this IP header conversion, the IP headerconverting unit 6 makes an inquiry of the IP address conversioninformation holding unit 4, thereby acquiring the IPv4 multicast addresscorresponding to the IPv6 transmission destination address of the IPv6multicast packet. Then, using the acquired IPv4 multicast address, theIP header converting unit 6 converts the IPv6 transmission destinationaddress of the above-described IPv6 multicast packet into the IPv4transmission destination address. The IP header converting unit 6 makesan inquiry of the IP address conversion information holding unit 4,thereby acquiring the IPv4 unicast address corresponding to the IPv6transmission source address of the IPv6 multicast packet. Then, usingthe acquired IPv4 unicast address, the IP header converting unit 6converts the IPv6 transmission source address of the above-describedIPv6 multicast packet into the IPv4 transmission source address.

FIG. 13 illustrates an example of the hardware configuration of theconverting apparatus illustrated in FIG. 1. In FIG. 13, the convertingapparatus 1 a includes the following devices: An IP-I/O device 133 forestablishing the connection with the IPv4 network 101 and the IPv6network 102, a storage device 135 including, for example, a RAM 131, aROM 132, and so on, and an arithmetic-logic device 130 for executingprograms stored in the storage device 135 and performing the processingof various types of data stored in the storage device 135. The IP-I/Odevice 133, the storage device 135, and the arithmetic-logic device 130are connected to each other through a bus 134 or the like. Here, inaddition to the RAM 131 and the ROM 132, the converting apparatus 1 amay have the other storage device such as a hard disk. In this case, theother storage device such as the hard disk is not necessarily-connecteddirectly to the bus 134.

The IP transmitting/receiving unit 2 illustrated in FIG. 1 includes theIP-I/O device 133, i.e., a network interface for performing thetransmittance/reception of the IP (i.e., Internet Protocol) packets inFIG. 13, a program that is held in the storage device 135 and is neededfor the operation of the IP transmitting/receiving unit 2, and thearithmetic-logic device 130 for executing the program. Also, the IP-I/Odevice 133 may perform the transmittance/reception processing of thepackets for the IPv4 network 101 and the IPv6 network 102 in thefollowing configuration: The IP-I/O device 133 is not controlled by thearithmetic-logic device 130 positioned in the different place, but theIP-I/O device 133 itself has the arithmetic-logic device 130 and thestorage device 135 inside.

Each of the for-conversion IP address holding unit 3, the IP addressconversion information holding unit 4, the IP multicast membership groupmanaging unit 5, and the IP header converting unit 6 illustrated in FIG.1 includes a program that is held in the storage device 135 and isneeded for the operation of each unit, and the arithmetic-logic device130 for executing the program.

FIG. 2 illustrates the configuration diagram of the IPv4 unicast addresstable 31. The IPv4 unicast addresses used for the IP header conversionare registered in advance into the IPv4 unicast address table 31 inaccordance with the instruction from the manager of the convertingapparatus 1 a. It is assumed that, in FIG. 2, the IPv4 unicast addressesof 133. 144. 93. 100˜133. 144. 93. 200 have been registered into theIPv4 unicast address table 31 in accordance with the instruction fromthe manager.

FIG. 3 illustrates the configuration diagram of the IPv4 multicastaddress table 32. The IPv4 multicast addresses used for the IP headerconversion are registered in advance into the IPv4 multicast addresstable 32 in accordance with the instruction from the manager of theconverting apparatus 1 a. It is assumed that, in FIG. 3, the IPv4multicast addresses of 238. 0. 0. 100˜238. 0. 0. 200 have beenregistered into the IPv4 multicast address table 32 in accordance withthe instruction from the manager.

FIG. 4 illustrates the configuration diagram of the IPv6 unicast addresstable 33. The IPv6 unicast addresses used for the IP header conversionare registered in advance into the IPv6 unicast address table 33 inaccordance with the instruction from the manager of the convertingapparatus 1 a. It is assumed that, in FIG. 4, the IPv6 unicast addressesof 1 : : 100˜1 : : 200 have been registered into the IPv6 unicastaddress table 33 in accordance with the instruction from the manager.

FIG. 5 illustrates the configuration diagram of the IPv6 multicastaddress table 34. The IPv6 multicast addresses used for the IP headerconversion are registered in advance into the IPv6 multicast addresstable 34 in accordance with the instruction from the manager of theconverting apparatus 1 a. It is assumed that, in FIG. 5, the IPv6multicast addresses of ffle : : 100˜ffle : : 200 have been registeredinto the IPv6 multicast address table 34 in accordance with theinstruction from the manager.

FIG. 6 illustrates the configuration diagram of the IP addressconversion table 41. The IP address conversion table 41 holds the IPv4multicast addresses and the IPv6 multicast addresses in correspondencewith each other, the IPv4 multicast addresses being the IPv4transmission destination addresses of the IPv4 multicast packetsreceived by the converting apparatus 1 a, the IPv6 multicast addresseshaving been acquired from the for-conversion IP address holding unit 3by the instruction from the IP multicast membership group managing unit5. Moreover, the IP address conversion table 41 holds the IPv4 unicastaddresses and the IPv6 unicast addresses in correspondence with eachother, the IPv4 unicast addresses being the IPv4 transmission sourceaddresses of the IPv4 multicast packets received by the convertingapparatus 1 a, the IPv6 unicast addresses having been acquired from thefor-conversion IP address holding unit 3 by the instruction from the IPaddress conversion information holding unit 4.

Also, the IP address conversion table 41 holds the IPv6 multicastaddresses and the IPv4 multicast addresses in correspondence with eachother, the IPv6 multicast addresses being the IPv6 transmissiondestination addresses of the IPv6 multicast packets received by theconverting apparatus 1 a, the IPv4 multicast addresses having beenacquired from the for-conversion IP address holding unit 3 by theinstruction from the IP multicast membership group managing unit 5.Moreover, the IP address conversion table 41 holds the IPv6 unicastaddresses and the IPv4 unicast addresses in correspondence with eachother, the IPv6 unicast addresses being the IPv6 transmission sourceaddresses of the above-described IPv6 multicast packets, the IPv4unicast addresses having been acquired from the for-conversion IPaddress holding unit 3 by the instruction from the IP address conversioninformation holding unit 4.

FIG. 7 illustrates the configuration diagram of the IPv4 multicastmembership table 51. The IPv4 multicast addresses of the IPv4 multicastgroup, of which the converting apparatus 1 a has become a member inaccordance with the instruction from the manager of the convertingapparatus 1 a, are registered into the IPv4 multicast membership table51.

FIG. 8 illustrates the configuration diagram of the IPv6 multicastmembership table 52. The IPv6 multicast addresses of the IPv6 multicastgroup, of which the converting apparatus 1 a has become a member inaccordance with the instruction from the manager of the convertingapparatus 1 a, are registered into the IPv6 multicast membership table52.

The respective tables that have been presented in FIGS. 2 to 8 so farare stored into, for example, the respective corresponding storageregions of the storage device 135 in accordance with the

FIG. 9 illustrates the schematic diagram of a communications networksystem where the IPv4 network 101 and the IPv6 network 102 are connectedto each other through the converting apparatus 1 a. An IPv4 multicastserver 104 and an IPv4 multicast client 105 are connected to the IPv4network 101. Here, the IPv4 multicast server 104 broadcasts (transmits)a multicast packet in compliance with IPv4, and the IPv4 multicastclient 105 receives the multicast packet in compliance with IPv4.Similarly, an IPv6 multicast server 106 and an IPv6 multicast client 107are connected to the IPv6 network 102. Here, the IPv6 multicast server106 broadcasts (transmits) a multicast packet in compliance with IPv6,and the IPv6 multicast client 107 receives the multicast packet incompliance with IPv6.

Here, the following assumptions are made concerning the addressassignment: An IPv4 address 133. 144. 93. 1 and an IPv6 address 1 : : 1have been assigned to the converting apparatus 1 a. Also, an IPv4address 133. 144. 93. 2 has been assigned to the IPv4 multicast server104. Also, an IPv4 address 133. 144. 93. 3 has been assigned to the IPv4multicast client 105. Also, an IPv6 address 1 : : 2 has been assigned tothe IPv6 multicast server 106. Also, an IPv6 address 1 : : 3 has beenassigned to the IPv6 multicast client 107.

Also, the following assumptions are made: The IPv4 multicast server 104broadcasts (transmits), to the IPv4 network 101, an IPv4 multicastpacket the destination address of which is an IPv4 multicast address(238. 0. 0. 1). Similarly, the IPv6 multicast server 106 broadcasts(transmits), to the IPv6 network 102, an IPv6 multicast packet thedestination address of which is an IPv6 multicast address (ffle : : 1).

Additionally, in FIG. 9, the IPv4 network 101 and the IPv6 network 102are physically isolated completely. However, even in the case where theIPv4 network 101 and the IPv6 network 102 exist in a mixed manner withinthe physically same network, the explanation given below concerning theembodiment guarantees that the converting apparatus 1 a will function inmuch the same way.

FIGS. 10 and 11 illustrate a flowchart in the following case: Using theIPv4 multicast address of 238. 0. 0. 1 as the destination address, theIPv4 multicast server 104 broadcasts (transmits) the IPv4 multicastpacket to the IPv4 network 101. Next, the converting apparatus 1 areceives the IPv4 multicast packet so as to subject the packet to the IPheader conversion processing, then sending out the converted packet tothe IPv6 network 102.

The IPv4 multicast server 104 broadcasts (transmits), to the IPv4network 101, the IPv4 multicast packet the destination address of whichis the IPv4 multicast address of 238. 0. 0. 1 (FIG. 10).

In order to relay the IPv4 multicast packet to the IPv6 network 102 byconverting the IPv4 multicast packet into the IPv6 multicast packet, themanager of the converting apparatus 1 a instructs the IP multicastmembership group managing unit 5 to make the converting apparatus 1 abecome a member of the multicast group of the IPv4 multicast address(238. 0. 0. 1).

Having received the instruction from the manager, the IP multicastmembership group managing unit 5, at first, registers the IPv4 multicastaddress (238. 0. 0. 1) into the IPv4 multicast membership table 51.Next, the IP multicast membership group managing unit 5 instructs the IPaddress conversion information holding unit 4 to register the IPv4multicast address (238. 0. 0. 1) and the IPv6 multicast addresscorresponding thereto into the IP address conversion table 41.

The IP address conversion information holding unit 4 searches the IPaddress conversion table 41 with the IPv4 multicast address (238. 0. 0.1). If the applicable entry has been found out, the IP addressconversion information holding unit 4 makes a report to the effecttoward the IP multicast membership group managing unit 5. If noapplicable entry has been found out, the IP address conversioninformation holding unit 4 acquires the IPv6 multicast address from thefor-conversion IP address holding unit 3, then registering, into the IPaddress conversion table 41, the IPv6 multicast address in a state ofbeing made to correspond to the IPv4 multicast address (238. 0. 0. 1).Moreover, toward the IP multicast membership group managing unit 5, theIP address conversion information holding unit 4 makes a report to theeffect that the IPv4 multicast address (238. 0. 0. 1) and the IPv6multicast address corresponding to this address have been registeredinto IP address conversion table 41. At this step in FIG. 10, since noapplicable entry has been found out, the IP address conversioninformation holding unit 4 acquires the IPv6 multicast address (ffle : :100) from the for-conversion IP address holding unit 3 so as to registerthe IPv6 multicast address into the IP address conversion table 41 incorrespondence with the IPv4 multicast address (238. 0. 0. 1), thenmaking the report to the effect toward the IP multicast membership groupmanaging unit 5.

Having received from the IP address conversion information holding unit4 the report to the effect that the entry corresponding to the IPv4multicast address (238. 0. 0. 1) has been registered into IP addressconversion table 41, the IP multicast membership group managing unit 5instructs the IP transmitting/receiving unit 2 to transmit, to the IPv4network 101, an “IGMP (i.e., Internet Group Management Protocol)Membership Report” message for indicating the membership into the IPmulticast group of the IPv4 address (238. 0. 0. 1).

In accordance with the instruction from the IP multicast membershipgroup managing unit 5, the IP transmitting/receiving unit 2 transmitsthe “IGMP Membership Report” message to the IPv4 network 101.

This allows the converting apparatus 1 a to receive the IPv4 multicastpacket that the IPv4 multicast server 104 broadcasts (transmits) to theIPv4 network 101 with the use of the IPv4 multicast address of 238. 0.0. 1. Subsequently, the converting apparatus 1 a executes the followingprocessing, which is illustrated in FIG. 11.

The converting apparatus 1 a receives the IPv4 multicast packet from theIPv4 network 101 through the IP transmitting/receiving unit 2. The IPtransmitting/receiving unit makes an inquiry of the IP multicastmembership group managing unit 5 about whether or not the convertingapparatus 1 a has become a member of the multicast group of the IPv4destination address of the IPv4 multicast packet that the convertingapparatus 1 a has received. The

The IP multicast membership group managing unit 5 checks whether or notthe IPv4 destination address of the received IPv4 multicast packet hasbeen registered in the IPv4 multicast membership table 51, then making areport on the result (i.e., membership-completed/membership-uncompleted)toward the IP transmitting/receiving unit 2. At this step in FIG. 11,since the IPv4 address of 238. 0. 0. 1 has been registered in the IPv4multicast membership table 51, the IP multicast membership groupmanaging unit 5 makes, toward the IP transmitting/receiving unit 2, thereport to the effect of having been membership-completed.

When receiving from the IP multicast membership group managing unit 5the report of having been membership-uncompleted, the IPtransmitting/receiving unit 2 disposes the IPv4 multicast packet. Whenreceiving from the IP multicast membership group managing unit 5 thereport of having been membership-completed, the IPtransmitting/receiving unit 2 transfers the IPv4 multicast packet to theIP header converting unit 6. At this step in FIG. 11, since the IPtransmitting/receiving unit 2 has received the report of having beenmembership-completed, the IP transmitting/receiving unit 2 transfers theIPv4 multicast packet to the IP header converting unit 6.

Having received the IPv4 multicast packet from the IPtransmitting/receiving unit 2, the IP header converting unit 6 makes aninquiry of the IP address conversion information holding unit 4 aboutthe IPv6 address corresponding to the IPv4 destination address and theIPv6 address corresponding to the IPv4 source address.

First, the IP address conversion information holding unit 4 checkswhether or not the IPv4 destination address has been registered in theIP address conversion table 41. If the IPv4 destination address has beenregistered therein, the IP address conversion information holding unit 4makes, toward the IP header converting unit 6, a report on the IPv6multicast address corresponding to the IPv4 destination address. If theIPv4 destination address has not been registered in the IP addressconversion table 41, the IP address conversion information holding unit4 makes, toward the IP header converting unit 6, a report to the effectof having not been registered. Here, since the IPv4 destination address(238. 0. 0. 1) has been registered in the IP address conversion table41, the IP address conversion information holding unit 4 makes, towardthe IP header converting unit 6, the report on the IPv6 multicastaddress corresponding thereto (ffle : : 100).

Next, the IP address conversion information holding unit 4 checkswhether or not the IPv4 source address has been registered in the IPaddress conversion table 41. If the IPv4 source address has beenregistered therein, the IP address conversion information holding unit 4makes, toward the IP header converting unit 6, a report on the IPv6unicast address corresponding to the IPv4 source address. If the IPv4source address has not been registered in the IP address conversiontable 41, the IP address conversion information holding unit 4 acquiresthe IPv6 unicast address from the for-conversion IP address holding unit3. Moreover, after registering the acquired IPv6 unicast address and theIPv4 source address in correspondence with each other into the IPaddress conversion table 41, the IP address conversion informationholding unit 4 makes a report on the registered IPv6 unicast addresstoward the IP header converting unit 6. At this step in FIG. 11, sincethe IPv4 source address (133. 144. 93. 2) has not been registered in theIP address conversion table 41, the IP address conversion informationholding unit 4 acquires the IPv6 unicast address (1 : : 100) from thefor-conversion IP address holding unit 3 so as to register the IPv6unicast address into the IP address conversion table 41. After that, theIP address conversion information holding unit 4 makes the report on theIPv6 unicast address (1 : : 100) toward the IP header converting unit 6.

The IP header converting unit 6 receives, from the IP address conversioninformation holding unit 4, the reports on the IPv6 multicast addressand the IPv6 unicast address that correspond to the IPv4 destinationaddress of the received IPv4 multicast packet and the IPv4 sourceaddress thereof, respectively. Moreover, the IP header converting unit 6creates the IPv6 multicast packet from the received IPv4 multicastpacket by the IP header conversion, then instructing the IPtransmitting/receiving unit 2 to send out the created IPv6 multicastpacket to the IPv6 network 102. In the IP header conversion, the IPheader converting unit 6 converts the IPv4 destination address into theIPv6 multicast address corresponding thereto, and converts the IPv4source address into the IPv6 unicast address corresponding thereto. Whenthe IP header converting unit 6 has received, from the IP addressconversion information holding unit 4, the report to the effect that theIPv4 destination address of the received IPv4 multicast packet has notbeen registered in the IP address conversion table 41, the IP headerconverting unit 6 disposes the received IPv4 multicast packet. At thisstep in FIG. 11, the IP header converting unit 6 has received, from theIP address conversion information holding unit 4, the reports on theIPv6 multicast address (ffle : : 100) corresponding to the IPv4destination address (238. 0. 0. 1) and the IPv6 unicast address (1 : :100) corresponding to the IPv4 source address (133. 144. 93. 2).Furthermore, the IP header converting unit 6 converts the IPv4destination address (238. 0. 0. 1) into the IPv6 destination address(ffle : : 100) using the IPv6 multicast address, and converts the IPv4source address (133. 144. 93. 2) into the IPv6 source address (1 : :100) using the IPv6 unicast address. By executing the above-describedprocessing, the converting apparatus 1 a creates the IPv6 multicastpacket from the IPv4 multicast packet. In addition, the convertingapparatus 1 a sends out the created IPv6 multicast packet to the IPv6network 102 through the IP transmitting/receiving unit 2.

The IPv6 multicast client 107 becomes a member of the IPv6 multicastgroup of the IPv6 destination address (ffle : : 100) of the IPv6multicast packet created by the converting apparatus 1 a. Thismembership makes it possible for the IPv6 multicast client 107 toreceive this IPv6 multicast packet.

The above-described processing permits the IPv6 multicast client 107 toreceive the IP multicast packet that the IPv4 multicast server 104broadcasts (transmits) to the IPv4 network 101 with the IPv4 address of238. 0. 0. 1.

In this embodiment, the explanation has been given regarding the casewhere the IPv6 multicast client 107 receives the IPv4 multicast packetthat the IPv4 multicast server 104 broadcasts (transmits) to the IPv4network 101 with the IPv4 address of 238. 0. 0. 1. Meanwhile, in thecase as well where the IPv4 multicast client 105 receives the IPv6multicast packet that the IPv6 multicast server 106 broadcasts(transmits) to the IPv6 network 102 using the IPv6 multicast address offfle : : 1 as the destination address, it is allowable to cause theconverting apparatus 1 a to execute the same processing in order toaccomplish the object. Namely, first, the converting apparatus 1 abecomes a member of the group of the IPv6 multicast packet that the IPv6multicast server 106 broadcasts (transmits) to the IPv6 network 102. Onaccount of this, the IP multicast membership group managing unit 5instructs the IP transmitting/receiving unit 2 to transmit, to the IPv6network 102, a “Multicast Listener Report” message described in, forexample, RFC (i.e., Request For comments) 2710. This permits theconverting apparatus 1 a to receive the IPv6 multicast packet that theIPv6 multicast server 106 broadcasts (transmits) to the IPv6 network 102using the IPv6 multicast address of ffle : : 1.

The IP header converting unit 6 converts the IPv6 destination address(ffle : : 100) of the IPv6 multicast packet into the IPv4 multicastaddress held in the IP address conversion table 41 in correspondencewith the IPv6 multicast address, and converts the IPv6 source addressinto the IPv4 unicast address held in the IP address conversion table 41in correspondence with the IPv6 unicast address. Moreover, theconverting apparatus 1 a causes the IP header converting unit 6 tosubject the IPv6 multicast packet received from the IPv6 network 102 tothe IP header conversion processing by the IP header converting unit 6.

Furthermore, the converting apparatus 1 a sends out the created IPv4multicast packet to the IPv4 network 101 through the IPtransmitting/receiving unit 2. The above-described processing permitsthe IPv4 multicast client 105 to receive the IPv4 multicast packetcreated and sent out to the IPv4 network 101 by the converting apparatus1 a.

In this embodiment, the converting apparatus 1 a has executed the IPheader conversion toward the IPv4 multicast packet indicated by themanager. Other than this, it is also allowable to employ theconfiguration where the converting apparatus 1 a executes the IP headerconversion toward the IPv4 multicast packet that the convertingapparatus 1 a has automatically detected by monitoring the IPv4 network101. Similarly, it is also allowable to employ the configuration wherethe converting apparatus 1 a executes the IP header conversion towardthe IPv6 multicast packet that the converting apparatus 1 a hasautomatically detected by monitoring the IPv6 network 102.

In this embodiment, the explanation has been given regarding the casewhere the IPv4 destination address (238. 0. 0. 1) of the IPv4 multicastpacket that the IPv4 multicast server 104 broadcasts (transmits) to theIPv4 network 101 is converted into the IPv6 multicast address (ffle : :100) acquired from the for-conversion IP address holding unit 3. Otherthan this, the IPv4 destination address (238. 0. 0. 1) of the IPv4multicast packet that the converting apparatus 1 a has received is alsoallowed to be converted into a 128-bit IPv6 address resulting fromadding a fixed pattern to the higher-order bits of the IPv4 destinationaddress (e.g., ffle : : ffff : 238. 0. 0. 1).

In this embodiment, the explanation has been given regarding the casewhere, as illustrated in FIG. 9, the-converting apparatus 1 a and theIPv4 multicast server 104 are connected to the same IPv4 network 101.Other than this, as illustrated in FIG. 12, the case is also allowablewhere the converting apparatus 1 a and the IPv4 multicast server 104 areconnected to different IPv4 networks. In this case, the IGMP messagethat the converting apparatus 1 a transmits in order to become themember of the IPv4 address of 238. 0. 0. 1 is received by an IPv4multicast router 121. Then, a multicast routing protocol operatesbetween the IPv4 multicast router 121 and an IPv4 multicast router 122,thereby causing the IPv4 multicast packet to be transferred from theIPv4 multicast server 104 up to the converting apparatus 1 a. The caseis also allowable where the converting apparatus 1 a and the IPv6multicast server 104 are connected to different IPv6 networks.

The present embodiments allow the IP multicast communication to beexecuted between the IPv4 terminal and the IPv6 terminal. As a result,it becomes possible for the IPv6 terminal to receive the IP multicastpacket that is broadcast (transmitted) from the IPv4 terminal. Also, itbecomes possible for the IPv4 terminal to receive the IP multicastpacket that is broadcast (transmitted) from the IPv6 terminal.

1. A method of relaying multicast packet in a converting apparatuslocated between an IPv4 network and an IPv6 network for realizing IPmulticast packet communication between an IPv4 terminal connected tosaid IPv4 network and a plurality of IPv6 terminals connected to saidIPv6 network, comprising the steps of: receiving an instruction tobecome a member of a multicast group of an IPv4 multicast address whichis a destination address of an IPv4 multicast packet to be relayed;storing said IPv4 multicast address of said multicast group whichreceived said instruction and an IPv6 multicast address held in saidconverting apparatus in a manner that said IPv4 multicast address ofsaid multicast group is correlated to said IPv6 multicast address heldin said converting apparatus; receiving an IPv4 multicast packetincluding said IPv4 multicast address as the destination address fromsaid IPv4 terminal connected to said IPv4 network; converting said IPv4multicast address to said IPv6 multicast address that is correlatedthereto and stored in said converting apparatus; creating an IPv6multicast packet including said IPv6 multicast address as thedestination address from said IPv4 multicast packet; transmitting saidIPv6 multicast packet created to said plurality of IPv6 terminalsconnected to said IPv6 network; and discarding a received IPv4 multicastpacket when the IPv4 multicast address which is a destination address ofthe received IPv4 multicast packet is not stored.
 2. A method ofrelaying multicast packet according to claim 1, wherein said step ofconverting comprises a step of converting an IPv4 unicast addressincluded as a transmission source address in said IPv4 multicast packetto an IPv6 unicast address.
 3. A method of relaying multicast packetaccording to claim 2, further comprising the steps of: holding at leastone of the IPv6 unicast addresses; and assigning an optional IPv6unicast address among said IPv6 unicast addresses held to said IPv4unicast address and storing said IPv4 unicast address in correspondencewit said optional IPv6 unicast address, wherein said step of convertingcompromises a step of converting said IPv4 unicast address to saidoptional IPv6 unicast address stored in correspondence with said IPv4unicast address.
 4. A method of relaying multicast packet according toclaim 2, wherein said step of converting comprises a step of adding afixed pattern of 96 bits to said IPv4 unicast address so that said IPv4multicast address is converted to said IPv6 multicast address.
 5. Amethod of relaying multicast packet from at least one of a firstapparatus which executes communication using IPv4 to at least one of asecond apparatus which executes communication using IPv6, comprising thesteps of: receiving an instruction to become a member of a multicastgroup of a first IPv4 multicast address which is a destination addressof an IPv4 multicast packet to be relayed; storing said first IPv4multicast address of said multicast group which received saidinstruction and an optional IPv6 multicast address in a manner that saidfirst IPv4 multicast address of said multicast group is correlated tosaid IPv6 multicast address; receiving an IPv4 multicast packettransmitted from an optional apparatus of said first apparatus;examining as to whether or not a second IPv4 multicast address includedas a destination address in said received IPv4 multicast packetcorresponds to said stored first IPv4 multicast address; when saidsecond IPv4 multicast address corresponds to said stored first IPv4multicast address, converting said second IPv4 multicast address to saidIPv6 multicast address correlated thereto and stored in said convertingapparatus; creating an IPv6 multicast packet including said IPv6multicast address as a destination address from said IPv4 multicastpacket received; transmitting said IPv6 multicast packet created; andwhen said second IPv4 multicast address does not correspond to saidstored first IPv4 multicast address, discarding the received second IPv4multicast packet.
 6. A method of relaying multicast packet according toclaim 5, wherein said step of converting comprises a step of convertingan IPv4 unicast address included as a transmission source address insaid IPv4 multicast packet received to an IPv6 unicast address.
 7. Amethod of relaying multicast packet according to claim 6, furthercomprising the steps of: holding at least one of IPv6 unicast addresses;and assigning an optional IPv6 unicast address among said IPv6 unicastaddresses held to said IPv4 unicast address and storing said IPv4unicast address in correspondence with said optional IPv6 unicastaddress, wherein said step of converting comprises a step of convertingsaid IPv4 unicast address to said optional IPv6 unicast address storedin correspondence with said IPv4 unicast address.
 8. A method ofrelaying multicast packet according to claim 6, wherein said step ofconverting comprises a step of adding a fixed pattern of 96 bits to saidIPv4 unicast address so that said IPv4 multicast address is converted tosaid IPv6 multicast address.
 9. A method of relaying multicast packetfrom at least one of a first apparatus which executes communicationusing IPv4 to at least one of a second apparatus which executescommunication using IPv6, comprising; storing at least one IPv4multicast address which is a destination address of an IPv4 multicastpacket to be relayed to said second apparatus; receiving an IPv4multicast packet transmitted from an optional apparatus of said firstapparatus; examining as to whether or not a second IPv4 multicastaddress included as a destination address in said IPv4 multicast packetreceived is included in said first IPv4 multicast address stored; whensaid second IPv4 multicast address is included in said first IPv4multicast address stored, converting said second IPv4 multicast addressto an IPv6 multicast address; creating an IPv6 multicast packetincluding said IPv6 multicast address as a destination address from saidIPv4 multicast packet received; and transmitting said IPv6 multicastpacket created, wherein said step of examining comprises a step ofdiscarding said IPv4 multicast packet received, when said second IPv4multicast address is not included in said first IPv4 multicast addressstored.